JP2022037084A - Method and system for detecting leaks in fluid system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and system for detecting leaks in a fluid system.

SOLUTION: A method of detecting leaks in a fluid system comprises determining an outflow amount of at least one first fluid within a certain time interval, determining an expected consumption of the first fluid during the certain time interval, determining a difference between the determined outflow amount and the determined expected consumption (step 44), and detecting a leak on the basis of a comparison between a reference value and the determined difference (step 46).

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to the method described in the premise of the independent method claim, the system described in the premise of the independent system claim, and the fuel cell system described in the premise of the parallel independent system claim.

Methods and systems for detecting leaks in fluid systems are known in the art.

For this purpose, pressure sensors are usually placed in various areas of the fluid system, which monitor the system pressure in proper operating conditions and leak in both steady and unsteady states. Can be detected. In steady states with no gas flowing, leaks are usually confirmed on the basis of a rapid pressure drop. In contrast, during the operation of a fluid system in which a gas flow is generated, leaks are detected only by confirming the generation of pressure that is too low in the steady flow.

The object of the present invention is a method having the characteristics of the independent method claim, a system having the characteristics of the independent system claim, and a fuel cell system having the characteristics of the parallel type independent system claim. Other features and details of the invention are described in their respective dependent claims, specification and drawings. In this case, the features and details described in connection with the method according to the invention also apply, of course, to the system according to the invention and the fuel cell system according to the invention, and vice versa. May always be referred to each other in connection with the disclosure of.

The method according to the present invention described in the main claim is used for detecting a leak in a fluid system, preferably a fuel cell system, particularly a PEM fuel cell system. In this case, the advantage of this method is that it can reliably detect already small leaks, especially while the fluid system is in operation. This is not possible with conventional methods for detecting leaks. Traditional methods can reliably detect only medium to large leaks in the active state. In this case, especially in the PEM fuel cell system, high system airtightness is an important factor for safety. This is because hydrogen is a flammable gas and is usually present in large quantities in PEM fuel cells.

In this case, the method according to the invention for detecting a leak in a fluid system can be used in a suitable form for a vehicle, particularly a fuel cell vehicle. Specifically, in the method according to the present invention, first, the first outflow amount of at least one first fluid is calculated within a predetermined time interval. In this case, the calculation of the outflow amount of the first fluid may be performed directly or indirectly. For direct calculations, for example, fluid flow is determined via a fill level indicator or flow meter. According to the indirect method, the runoff amount can also be determined indirectly from various other parameters, preferably measured. In this case, the time interval may be freely selected in a suitable format. In a preferred format, at the same time as the calculation of the outflow of the first fluid, specifically the predicted consumption of the first fluid is calculated. Instead of the simultaneous calculations, the predicted consumption may be calculated before or after the calculation of the first fluid runoff.

However, for the most compelling comparison between the calculated runoff and the calculated predicted consumption, in a suitable format, the time intervals between the calculations are located as close to each other in time as possible. Should be, and preferably the same. In addition, the time intervals should be approximately the same length for the most compelling comparison between the calculated runoff or the calculated predicted consumption. Optionally, the two calculated values may be determined at shorter time intervals if the corresponding extrapolation method is then performed over a longer time interval.

After calculating the runoff of the first fluid and after calculating the predicted consumption of the first fluid, specifically, the difference between the calculated runoff of the first fluid and the calculated predicted consumption. Is calculated. In this case, the calculation of the difference may be performed directly from the individual values or based on the values averaged for the first time after the calculation of a predetermined number of individual values. Then, after the calculation of the difference in time, the leakage is detected, and the leakage is specifically determined based on the comparison between the calculated difference and the reference value. In this case, the reference value is a system-dependent constant value in a suitable form, which may take into account measurement inaccuracies in some cases. Therefore, the reference value is ideally 0, assuming the system is completely airtight and there are no measurement inaccuracies. Therefore, in this case, the difference between the predicted consumption and the outflow of the first fluid is also not confirmed.

However, this may be considered in advance based on certain reference values, as no completely airtight system exists and measurement inaccuracies are unavoidable in some cases. In the meantime, the comparison between the reference value and the calculated difference may be made in various formats. In the simplest case, the comparison is based on the mere difference between the reference value and the calculated difference, in which case the leak can be detected, especially if it deviates from the reference value by at least a predetermined limit. Tolerance factors or tolerance ranges may also be added to this detection method within the framework of a particularly flexible detection method that can be used in a variety of systems and takes into account individual environmental conditions. When using the tolerance factor, the tolerance factor can be determined depending on external and system conditions, for example, because the leak is only detected when the product of the deviation and the tolerance factor exceeds the limit value. Optionally, when using a tolerance range, leaks can only be detected, for example, when the sum of the deviation and the tolerance range exceeds the limit. In a more preferred format, steps 1 to 4 of the specific method may be periodically repeated to ensure continuous inspection of the leak. In order to improve the persuasiveness of this method and, in some cases, to improve the accuracy of this method, even if only the individual steps of this method are repeated multiple times before the corresponding next step is started. good.

In a preferred manner, within the framework of the invention, the calculation of the outflow of at least one first fluid is at least partially based on pressure and / or temperature measurements of the first fluid. It's okay. In this case, the determination of the outflow amount based on the pressure measurement and / or the temperature measurement promises not only a simple and flexible calculation form of the outflow amount of the fluid but also an accurate calculation form at the same time. Especially in highly volatile gases, volume determination based on, for example, filling level display, floating, flowmeter is often erroneous. This is because the density of the fluid in the container changes depending on the composition of the fluid, which can cause a deviation in the volume determination. In contrast, according to pressure and / or temperature measurements, the fluid volume can be calculated, for example, at two different time points and can be determined at different time points with different outflows through the difference in fluid volume. Therefore, in a PEM fuel cell, for example, the amount of hydrogen outflow can be determined via the volume difference. In this case, the volume of hydrogen may be constructed as follows:
V (H ₂ ) = p / p ₀ ^* T / T ₀ ^* V ₀
In this equation, P ₀ and T ₀ represent atmospheric pressure (1.013 ^{* 106} Pa) or room temperature (298.15K), and V ₀ represents the net volume of the tank. From the volume difference of hydrogen at two different time points, the volume of hydrogen that has flowed out (converted to the standard conditions) is obtained, and the mass or amount of substance of the hydrogen that has flowed out is finally selected from the volume of hydrogen that has flowed out. Can be calculated in.

In connection with the calculation of the predicted consumption of the first fluid, further within the framework of the present invention, this calculation is based on the generated current and / or to the outflow detected from the drain valve or bleed valve. It may be at least partially done based on and / or on the basis of characteristic values for the fluid system. In this case, a particularly simple calculation is obtained by calculating the predicted consumption of the first fluid from the measured current or the charge passed through. In this case, the consumption of the fluid is obtained according to the stoichiometry of the reaction. In a PEM fuel cell, for example, 2 coulombs of measured charge correspond to 1 mol of substance of hydrogen. This amount of substance may be appropriately converted back into the volume or mass of the corresponding fluid.

In addition to calculations based on the measured current or the charge passed, additional outflow from the drain or bleed valve to make a particularly precise determination of the predicted consumption of the first fluid and prevent error warnings. Inclusion can be meaningful. For example, if oxygen that is not really sufficient for this is supplied to the other side of the fuel cell, it can happen that some of the hydrogen is not converted at all during the reaction. In this case, the amount of hydrogen that is intended to be predicted, calculated solely from the measured current or the charge that has passed, is significantly less than the amount that actually flows out, so the amount of outflow from the discharge valve or air bleeding valve without modification. By additionally including, leaks will be detected despite the complete sealing of the system, which will trigger an error warning. Gas outflow from the exhaust valve or air bleeding valve can be determined from valve characteristics, temperature and differential pressure, or without opening the exhaust valve or air bleeding valve.

To further optimize this specific method, within the framework of the embodiments of the method of the invention, which is particularly accurate and flexiblely adaptable to various systems, the calculation of the predicted consumption of the first fluid. At least in part, may be based on characteristic values for the fluid system. In this case, the characteristic values for the fluid system may be constant, or may be determined or measured continuously or periodically. In this case, in order to incorporate system-specific, fluid-specific or environmental condition-specific values into the calculation, the inclusion of characteristic values for the fluid system is specifically based on the measured current or the charge passed through the first fluid. It may be meaningful to do this in combination with the calculation of the predicted consumption of and in combination with the inclusion of the outflow from the exhaust valve or air bleeding valve. Thus, characteristic values for fluid systems may be applied, for example, to a stack model (of a fuel cell) or individual stacks, within the framework of system-specific values, and may be related to, for example, the conversion rate of the system. Within the framework of fluid-specific values, these characteristic values may be associated, for example, with respect to fluid density or volatility, flammability, ignitability or toxicity. Within the framework of values specific to environmental conditions, the characterized values may be associated with, for example, outside air temperature, outside pressure, and the like.

In addition to maximizing system airtightness, to ensure as economical operation as possible, the present invention further allows this method to be carried out in a reliable manner while the fuel cell system is in operation. Reliable leak detection during operation is desired, especially when using dangerous substances such as flammable, ignitable, flammable or potentially health hazards, based on their safety importance. There is. Otherwise, instead of reliable leak detection during operation, only one steady-state test remains here. The operation of the fluid system will, of course, be significantly limited in order for reliable testing of leaks to be performed only in steady state. This is because if the leaks that occur in some cases are preferably monitored periodically, the operation must be interrupted at regular time intervals in order to perform a reliable leak test. Within the framework of the present invention, the detection of smaller leaks is already less than 100 standard ml leaks at each connection point and time, preferably less than 50 standard ml per connection point and time, especially each connection. Leaks less than 20 standard ml per location and time are considered a reliable method.

Also, in order to further optimize the reliability of the method according to the invention, the method of at least one second fluid to detect leaks in addition to runoff and predicted consumption of the first fluid. It is conceivable to consider at least one parameter, in particular the runoff and / or expected consumption of the second fluid. Including the parameters of the second fluid is particularly meaningful when the specific method does not include determining the amount of outflow from the drain valve or air bleed valve to detect a leak in the fluid system. Therefore, for example, by knowing the amount of the second fluid used, and by knowing the stoichiometry of the reaction, it is confirmed whether or not the stoichiometrically equal substance ratio of the reaction partner is used, thereby. The predicted consumption of the first fluid can be modified accordingly at unequal material ratios of the reaction partners. Further according to the present invention, in addition to the determination and predicted consumption of the outflow of the first fluid, and at least one parameter of the second fluid, another parameter, in order to further improve the reliability of leak detection. For example, the water content of the thin film and / or the water content of the starting system and / or the water content of the gas distribution structure and / or the ambient temperature and / or the ambient pressure may be considered.

In the preferred form, also within the framework of the invention, based on the comparison, preferably based on the difference between the reference value and the calculated difference between the runoff and the predicted consumption. In particular, the error may be displayed and / or the error resolution measure may be started when at least the limit value is exceeded. In this case, the error-resolving measure may be, in particular, at least a partial shutoff of the fluid system, in particular a complete shutoff. Instead of a partial or complete system shutdown, the error display will at least issue a warning message when the limit is exceeded within the bounds of a pure error display, and this warning message is a special feature for detecting leaks. May be started by another more accurate test.

Basically, the method according to the invention is carried out on the medium or high pressure side of the fuel cell system (medium pressure is about 9-13 bar / high pressure is about 350-700 bar), in which case the minimum leakage is this. It can already be detected early by the method.

Similarly, an object of the present invention is a system having the characteristics of claim 8 for detecting a leak in a fluid system, particularly a fuel cell system. In this case, specifically, the system has at least one sensor unit for detecting a value for calculating the outflow of at least one first fluid. Further, the system according to the present invention has a control unit for calculating the predicted consumption of the first fluid and calculating the difference between the calculated outflow amount and the calculated predicted consumption. Further, the specific system has at least one detection unit for detecting a leak based on a comparison between a reference value and a calculated difference. Thereby, the system according to the invention provides the same advantages as described in detail in connection with the method according to the invention. As already described in the embodiments of the method according to the invention, specific systems are provided to detect leaks in fluid systems, especially fuel cell systems, in a suitable manner. The advantage of the system according to the present invention is, in particular, that the system can reliably detect small leaks already, even in the active state of the fluid system. In order to control the system according to the present invention, the individual system components are connected to each other in a suitable manner via a control connection or a communication connection. In this case, the control connection or communication connection may be configured at least partially wirelessly and / or at least partially wired. In a preferred form, the control and / or communication connections may be connected to each other via a BUS system, in particular a CAN-BUS system.

Further, within the framework of the present invention, the system has an error display unit or an error resolution unit for displaying or eliminating an error, in which case the error display unit or the error resolution unit is in a suitable form. It is proposed to be activated when the margin for the difference between the difference calculated from the runoff and expected consumption and the reference value is exceeded. In this case, the error display element may be provided with a vibrator type and / or an auditory type and / or a visual type element. In this case, the error display may include, for example, all elements or only individual elements. Similarly, the display element may be determined by the magnitude of the shift. Therefore, in any case of small size, a vibrator type error display may be simply performed. In either case, the auditory error display may be performed exclusively, or the vibrator and auditory error display may be performed. In any of the larger cases, only the visual error display may be finally performed, or the auditory, vibrator and visual error display may be performed. Therefore, for the operator of the fluid system, the leaks and the magnitude of the leaks already detected can be revealed very early on. The error-resolving unit may specifically be provided with an emergency shutoff element for shutting off at least partial, preferably complete fluid systems.

Similarly, the subject of the invention is a fuel cell system, particularly a (fuel cell) vehicle, having the system according to the invention for carrying out the method according to the invention.

FIG. 3 is a schematic diagram of a system according to the invention for detecting leaks in a fluid system. FIG. 3 is a schematic representation of a method according to the invention for detecting leaks in a fluid system.

Other advantages, features and details of the invention are described in the following description detailing a plurality of embodiments of the invention with reference to the drawings. In this case, the features described in the claims and the specification are important to the present invention, either individually or in any combination.

In the drawings, the same reference numerals are used for the same technical features.

FIG. 1 shows a schematic diagram of a system 1 according to the invention for detecting leaks in a fluid system. The system 1 has a fuel cell having an anode 12 and a cathode 14, and the anode 12 and the cathode 14 are separated from each other by a membrane 16. In order to cool the fuel cell, a cooling unit 18 including a cooling circulation path 20 is arranged on the side of the cathode 14 of the fuel cell. Both the anode 12 and the cathode 14 are electrically connected to the membrane 16. During operation, the anode gas 2 flows around the anode 12 of the fuel cell, in which case the anode gas 2 is hydrogen. The hydrogen 2 is arranged in the container 2a, and the container 2a has a pressure sensor 8 for measuring the actual container pressure. By opening the shutoff valve 4, the hydrogen gas 2 is first guided into the high pressure region 22a of the anode gas pipeline 22. Here, first, the pressure measurement and the temperature measurement of the derived gas 2 are performed via the arranged pressure sensor 8 and the temperature sensor 10, and the amount of the hydrogen 2 derived from the result is determined. Due to the regulated opening of the metering valve 6, the anode gas 2 flows through the medium pressure region 22b of the anode gas pipeline 22 arranged behind the metering valve 6, and the actual hydrogen is entered in the medium pressure region 22b. Another pressure sensor 8'designed for the medium pressure range for measuring pressure is located. The gas finally reaches the anode 12 via another metering valve 6.

Cathode gas 2'on the opposite side of the anode gas 2, fresh air containing oxygen in this embodiment is introduced. The air 2'is sucked in and first filtered in the air filter 28. In this case, air filtration is used to protect the fuel cell components from harmful particulates and gaseous contaminants from the inhaled air. After filtration, the cathode gas 2'is compressed by the compressor 26 and guided through the shutoff valve 4 into the high pressure region 24a of the cathode gas pipeline 24, again within the high pressure region 24a and into the anode gas pipeline 22. Similarly, pressure measurement and temperature measurement are performed via the arranged pressure sensor 8 and temperature sensor 10. From the calculated pressure and temperature values, the amount of outflowed cathode gas 2'can be determined in the same way as the amount of outflowed anode gas 2 is determined. Next, the cathode gas 2'is guided into the medium pressure region 24b of the cathode gas pipeline 24 via the metering valve 6, and in this medium pressure region 24b, medium for measuring the actual pressure of the cathode gas pressure. Another pressure sensor 8'designed for about the pressure range is located. The cathode gas 2'is finally supplied to the cathode 14 via another metering valve 6. A lead-out line 22c or 24c is arranged on both the anode 12 side and the cathode 14 side, and the pressure in these lead-out lines 22c or 24c is determined via the pressure sensor 8 ″. The unconsumed residual gas and reaction product can be derived (controlled), in particular, by the provided isolation valve 4'through the pressure sensor of. In this case, the anode gas 2 not consumed during the reaction. , Newly supplied to the system via the appropriate pipeline in a suitable format.

FIG. 2 shows a schematic representation of a method according to the invention for detecting a leak in a fluid system 1 having steps 40-50. In step 40 or 42, at least the outflow of the first fluid 2 and the predicted consumption of the first fluid 2 are calculated at a suitable time within a predetermined time interval. Instead of the temporally simultaneous calculations, the predicted consumption may be calculated before or after the calculation of the outflow of the first fluid 2, in which case the time interval between calculations is calculated. In order to obtain the most compelling comparison between the runoff and the calculated expected consumption, they should be as close as possible to each other, thereby providing the same conditions as possible for the two calculations. In addition, the time intervals should be approximately the same length for the most compelling comparison between the calculated runoff or the calculated predicted consumption. Optionally, if the corresponding extrapolation method is then performed over a longer time interval, one of the two calculated values may be determined at a shorter time interval.

After the runoff amount is calculated and after the predicted consumption of the first fluid 2, the difference between the two values is calculated in step 44. In this case, the calculation of the difference may be performed directly from the individual values, or may be performed based on the mean value of these values only after the calculation of a predetermined number of values.

Finally, in step 46, the calculated difference between the runoff and the predicted consumption of the first fluid 2 is compared to the reference value and the leak is identified based on this comparison. In this case, the reference value is a system-dependent constant value, in a suitable form, in which measurement inaccuracies can be considered in some cases. Therefore, it can ideally be zero, assuming the system is completely airtight and there are no measurement inaccuracies. Therefore, in this case, it may be detected that there is no difference between the runoff amount and the predicted consumption of the first fluid. However, since there is no completely airtight system and measurement inaccuracies are unavoidable in some cases, this may be considered in advance based on certain reference values. Comparisons between reference values and calculated differences can be made in a variety of formats. In the simplest case, the comparison is based on a mere difference between the reference value and the calculated difference, in which case the leak is detected, especially if it deviates from the reference value by a predetermined limit. Additional tolerance factors or tolerance ranges may be added to this detection method within the framework of a particularly flexible detection method that can be used in a variety of systems and takes into account individual environmental conditions. When comparing the calculated difference between the runoff and the predicted consumption with the reference value, if a deviation above a predetermined limit is calculated, an error is displayed and / in step 48 or 50. Or error resolution measures are started. If the deviation does not exceed a predetermined limit value, steps 40 to 46 are newly executed. To ensure continuous inspection for leaks, steps 40-46 of the specific method are followed until the discrepancy between the reference value and the difference between the spill and the predicted consumption does not exceed the limit. It is particularly preferable if it is repeated periodically.

1 System, fluid system 2 1st fluid, anode gas 2'second fluid, cathode gas 2a container 4 shutoff valve 4'shutoff valve, exhaust valve or air bleeding valve 6 metering valve 8,8', 8 "pressure Sensor 10 Temperature sensor 12 anode 14 cathode 16 membrane 18 cooling unit 20 cooling circulation channel 22 anode gas pipeline 22a high pressure region 22b medium pressure region 22c outlet pipeline 24 cathode gas pipeline 24a high pressure region 24b medium pressure region 24c outlet pipeline 26 Compressor 28 Air filter 40, 42, 44, 46, 48, 50 steps

Claims (10)

In the method for detecting leaks in fluid systems,
A step of calculating the outflow amount of at least one first fluid (2) within a predetermined time interval, and
A step of calculating the predicted consumption of the first fluid (2) within a predetermined time interval, and
The step of calculating the difference between the calculated outflow amount and the calculated predicted consumption, and
The step of detecting a leak based on the comparison between the reference value and the calculated difference, and
A method for detecting leaks in a fluid system. Claim 1 is characterized in that the calculation of the outflow amount of at least one first fluid (2) is performed at least partially based on the pressure measurement and / or the temperature measurement of the first fluid (2). The method described. The calculation of the predicted consumption of the first fluid (2) is based on the generated current and / or the outflow detected from the exhaust valve or the air bleeding valve (4'), and / or of the fluid system. The method according to claim 1 or 2, wherein the method is performed at least partially based on the characteristic value for the purpose. The method according to any one of claims 1 to 3, wherein the method is used in a fluid system of a vehicle. The method according to any one of claims 1 to 4, wherein the method can be carried out in a reliable manner while the fuel cell system is in operation. The method is characterized by considering at least one parameter of at least one second fluid (2') to detect a leak in addition to the outflow and predicted consumption of the first fluid (2). The method according to any one of claims 1 to 5. Based on the comparison, optionally, display an error and / or initiate an error resolution measure based on the difference between the reference value and the calculated difference between the runoff and the predicted consumption. The method according to any one of claims 1 to 6, wherein the method is to be performed. In a system for detecting leaks in a fluid system
At least one sensor unit for detecting a value for calculating the outflow amount of at least one first fluid (2) within a predetermined time interval, and
At least one control unit for calculating the predicted consumption of the first fluid (2) within a predetermined time interval and calculating the difference between the calculated outflow amount and the calculated predicted consumption. When,
At least one detection unit for detecting a leak based on the comparison between the reference value and the calculated difference, and
A system for detecting leaks in fluid systems. The system has an error display unit or an error resolution unit for displaying or eliminating an error, and the error display unit or the error resolution unit is in a suitable format and is calculated from the outflow amount and the predicted consumption. The system of claim 8, wherein the system is activated when the limit value for the difference between the difference and the reference value is exceeded. A vehicle fuel cell system having the system according to claim 8 or 9.

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